(a) Field of the Invention
The present invention relates to an apparatus and a method for time synchronization and a reception apparatus of an orthogonal frequency division multiplexing (OFDM) system.
(b) Description of the Related Art
A vehicle communication system that provides vehicle-to-vehicle communication and vehicle-to-infrastructure communication on the basis of a vehicle moving at high speed uses an orthogonal frequency division multiplexing (hereinafter referred to as “OFDM”) scheme as a wireless LAN technology.
Since the vehicle communication system is designed assuming a wireless channel at a stoppage speed or a pedestrian speed, the performance of the system is remarkably deteriorated in a channel environment in which the vehicle moves at a high speed.
The OFDM-based wireless LAN system uses a preamble at the time of transmitting and receiving data signals. The preamble is constituted by a short training sequence and a long training sequence. A reception device detects a start point of a frame by using the short training sequence, and detects a frequency error and a channel phase error by using the long training sequence and compensates the errors. The short training sequence and the long training sequence are designed on the basis of a channel environment having a low movement speed, so it is difficult to detect an accurate frame and accurate synchronization and estimate a channel in the channel environment in which the vehicle moves at the high speed.
Further, as a master clock of the reception device, a clock operating at a double speed on the basis of a digital sampling rate of a transmission signal is used. In this case, since resolution is insufficient in acquiring a sample having maximum reception energy in the reception device, errors of a frame and symbol synchronization increase. When the errors of the frame and symbol synchronization increase, a demodulation function is performed by using a sample having low reception energy value, thereby deteriorating demodulation performance.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.